Voyager program (Mars) in the context of Viking program

The Viking program consisted of a pair of identical American space probes, Viking 1 and Viking 2 both launched in 1975, and landed on Mars in 1976. The mission effort began in 1968 and was managed by the NASA Langley Research Center. Each spacecraft was composed of two main parts: an orbiter spacecraft which photographed the surface of Mars from orbit, and a lander which studied the planet from the surface. The orbiters also served as communication relays for the landers once they touched down.

The Viking program grew from NASA's earlier, even more ambitious, Voyager Mars program, which was not related to the successful Voyager deep space probes of the late 1970s. Viking 1 was launched on August 20, 1975, and the second craft, Viking 2, was launched on September 9, 1975, both riding atop Titan IIIE rockets with Centaur upper stages. Viking 1 entered Mars orbit on June 19, 1976, with Viking 2 following on August 7.